A motion compensation compression technique refers to a technology for removing a temporal redundancy between successive video frames by using a motion estimation technique. A block-based motion estimation technique has been adopted in a compression standard of a video sequence such as MPEG-4, H.263 and the like.
The block-based motion estimation technique is widely used even in case of another compression standard due to its facility of implementation in hardware and/or software.
In the block-based motion estimation technique, each video frame is divided into a plurality of blocks, wherein each of the blocks is associated with a motion vector to describe a location change between a block in a reference video frame and that of a current video frame corresponding to the block in the reference video frame. The motion vector can be obtained from the location change of most similar blocks in the two frames. In other words, based on a block distortion measure (BDM) for calculating similarity between blocks, a block having a minimum BDM value is selected.
However, a currently used block-based motion estimation technique is considered to require a great amount of computation and much time therefor. To be specific, a full search motion estimation regarded to be comparatively accurate calculates a mean absolute deviation for every block in a search window of a predetermined size and selects a block having a minimum value thereof to thereby obtain a motion vector. In this case, a computational amount for the motion vector occupies more than 70% of that for an entire video compression.
To that end, a plurality of fast block-based motion estimation techniques have been suggested. However, such techniques are sub-optimal and do not provide as high of accuracy as the full search motion estimation technique because of an error caused by an assumption for applying an estimation method.